Error evaluation in the spectroscopic measurement of high power beam angular divergence

The broadening effects that play a role in spectrally resolved Doppler measurements of high power beams are analysed in relativistic conditions. A consistent study of error propagation assesses the accuracy in the beam angular divergence measurement and gives prescriptions in designing the beam emission spectroscopy diagnostic for the test bed facility of ITER neutral beam.

Research Highlights► The system dispersion affects the accuracy of high energy beam divergence measurement. ► High dispersions do not result in more accurate beam divergence measurements. ► The best choice for SPIDER BES is a plate of 0.007 nm/pixel and an obs. angle of 75°.